Ysley  

, イースリイ

Ysley is an Idaten who was born around 100 years ago due to a natural outbreak. He's known for being intelligent and prefers studying over fighting. Despite this, he began researching himself after realizing that he had been naturally born. Although he initially tried training under Rin, he quit after just two-three months because of her brutal methods. Ysley enjoys learning about past human civilizations and ruins. Following a magical being's appearance, he was defeated in the chest by it but Hayato managed to defeat this being. Recognizing that more demons would arise, Ysley decided to renew his training under Rin.